This invention relates to an interlock for controlling operation of a pair of switches, and more particularly to an interlock for controlling operation of a pair of aligned switches.
In many electrical installations, it may be desirable to provide simultaneous switching of electric switch handles, e.g., transfer switches. This may be found, for example, in an electrical distribution system that includes two power supplies, such as a primary power supply, such as utility power, and a backup power supply, such as an electrical generator. It is necessary to have a switching arrangement that controls the supply of power to the electrical distribution system. In one arrangement, each power supply is connected to a switch that is movable between an ON position that connects the power supply to the electrical distribution system and an OFF position that disconnects the power supply. The switches may be arranged in alignment with each other such that the switch handles are aligned. Provisions must be made to ensure that one power supply switch is in the OFF position when the other power supply is in the ON position and vice versa.
It is known to provide an interlock arrangement that functions to physically move one switch to the OFF position in response to movement of the other switch toward the ON position. Such mechanical interlocks are configured to make sure that each switch cannot be moved to its ON position before the other switch has been fully moved to its OFF position.
The present invention contemplates an interlock arrangement that introduces an additional step in the interlock process that requires an additional operation by a user before a switch can be placed in the ON position.